1. Field of the Invention
The present invention relates to an automotive air-conditioning system and more specifically, to an automotive air-conditioning system capable of diagnosing that each output device is properly operable or not.
2. Description of the Prior Art
A conventional automotive air-conditioning system is illustrated in FIG. 4. As shown in FIG. 4, it includes a duct 1 provided with a selector door 2 for selectively establishing the fresh air intake mode or the room air recirculating mode, a blower 3, a heat exchanger 4, an air mixing door 5, a heater door 6, mode changing doors 7, a window defrosting opening 8, a center opening 9 and a foot opening 10. The heat exchanger 4, a compressor 11, a condenser 12, a receiver tank 13 and an expansion valve 14 constitute a cooling system. The compressor 11 is connected through a magnetic clutch 16 to an engine 15. An analog to digital (A/D) converter 17 receives analog signals representing passenger compartment temperature or room temperature Tr detected by a room temperature sensor 18, an opening of the air mixing door 5 detected by a potentionmeter 19, intensity of insolation Ts detected by an insolation sensor 20, fresh air temperature Ta detected by a fresh air temperature sensor 21, heat exchanger temperature Tm detected by a heat exchanger temperature sensor 22 and a reference or set temperature TD provided by a temperature setting unit 23, and gives the corresponding digital signals to a control unit 24.
The control unit 24 is a computerized control unit comprising a selector door control means 27 for controlling the selector door 2 through a changeover circuit 25 and an actuator 26, a compressor control means 29 for controlling the magnetic clutch 16 through a driving circuit 28, a blower control means 31 for controlling the blower 3 through a driving circuit 30, an air mixing door control means 34 for controlling the air mixing door 5 through a driving circuit 32 and an actuator 33, a mode changing door control means 37 for controlling the mode changing doors 7 through a changeover circuit 35 and an actutor 36, and an arithmetic means 38 which processes the data corresponding to room temperature Tr, intensity of isolation Ts, fresh air temperature Ta, heat exchanger temperature Tm and set temperature TD and gives combined signals T to the control means 27, 29, 31, 34 and 37. Indicated at 39 is a manual switch for controlling the blower 3. The blower control means 31 controls the blower 3 depending on the status of operation.
The compressor control means 29 turns off the compressor 11 when the exchange temperature Tm is lowered to the temperature level L1 (stored in a setting unit) which is slightly higher than the freezing temperature of the heat exchanger 4, and turns on the compressor 11 when the temperature Tm is increased to the temperature level L2 (stored in a setting unit) which is higher in the range of hysteresis than the level L1 so that the temperature in the heat exchanger 4 is kept constant.
The setting unit or a manual switch 39 comprises an off-setting switch 39a, an automatic control setting switch 39b, a low speed setting switch 39c, a middle speed setting switch 39d and a high speed setting switch 39e. When the off-setting switch 39a is selected, the blower control means 31 stops the blower 3, when the automatic control setting switch 39b is selected, the blower control means 31 sets the speed of the blower to that corresponding to the combined signal T, when the low speed setting switch 39c is selected, the blower control means 31 sets the blower 3 to a low speed, when the middle speed setting switch 39d is selected, the blower control means 31 set the blower 3 to a middle speed, and when the high speed setting switch 39e is selected, the blower control means 31 sets the blower 3 to a high speed.
In the automotive air-conditioning system art, there is known Japanese Laid-Open Patent Publication No. 57-13520 which discloses a method to diagnose whether the output devices such as the selector door 2, the air mixing door 5, the mode changing doors 7, the compressor 11 and the like are properly operated or not. This is performed by driving each of the output devices in accordance with a sequential order based on a self-diagnosing program. This has however drawbacks that some time is required for diagnosing the output devices since some time is required until the output devices are actuated after operable status thereof has been diagnosed, and repetitive inspection of the same output devices is not performed.